Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~2~27 Case 5489/5681 (2)
PROCESS FOR UPGRADING HYDROCARBON FUELS
The present invention relate~ to a process for upgrading
hydrocarbon fuels for spark ignition internal combustion engines.
Internal combustion engines are so-called because they convert
the latent chemical energy of their fuels to useful power by burning
the fuels inside the engine. Both petrol engines and diesel engines
are examples of internal combustion engines and are mechanically
similar to the extent that both have cylinders and pistons connected
to a flywheel by a crankshaft, which converts the reciprocating act~on
of the piston caused by sequenced combustion of the ~uel to the rotary
action needed to power the driving wheels of the vehicle. The most
significant difference between the petrol and the diesel engine is the
way in which combustion is achieve~. In the petrol engine, a ~ixture
of petrol and air is drawn into the combustion chamber by the action
of the piston, or the petrol can be in~ected directly. As the piston
makes its return stroke, the mixture is compressed and then ignited by
an elèctric spark. In the diesel engine only air is drawn into the
combustion chamber. Once it has been compressed by the piston (to a
much higher pressure than in the petrol engine), diesel fuel is
~ in~ected into the combustion chamber, wherein it ignites spontaneously
due to the heat that has been generated by compression in the
cylinder. The present invention i8 concerned only with fuels for
spark ignition internal ~ombustion engines, as opposed to diesel
engines. The ter~ spark ignition engine includes not only the
aforesaid reciproca~ing piston type engine but also the rotary piston
engine, conventionally referred to as the Wankel engine, and any
modifications or variations of such angines~
~2~ 27
The combustion properties of the fuel are of prime importance to
engine performance. Thus petrol must volatilise, ignite easily and
burn progressively to ensure smooth combustion and efficient engine
performance. Spontaneous or premature explosion, giving rise to a
metallic knocking ("~nock") sound and to a loss of power, is
undesirable in pPtrol engines. A desirable property of a spark
ignition fuel is therefore a high knock resistance, which is measured
in terms of octane rating. The higher the octane rating, the higher
is the fuel's knock resistance. Another desirable property for a
spark ignition fuel is good volatility, the fuel must vapourise
adequately to form a readily combustible mixture in the combustion
chamber, but it must not be so volatile that it turns into a vapour in
the fuel system, otherwise a phenomenon called vapour lock will occur,
which manifests itself in the physical symptom of stalling.
US Patent No. 3,879,467 describes a method for the catalytic
oxidation of either straight chain, branched chain or cyclic C3 to C20
alkanes or mono-olefins to form alcohols and ketones using tertiary
butyl hydroperoxide in the presence of a chromium catalyst at
relatively low temperatures. Chromium catalysts are said to be
superior to other metal catalyst~ known to decompose hydroperoxides,
for example platinum, palladium, rhenium, thallium, thorium,
manganese, cobalt, iron, zirconium, nickel, zinc, cesium, copper,
antimony, bismuth, lead, arsenic, molybdenum, vanadium, tungsten and
titanium.
U~ Patent No. 4,104,036 describes an improved fuel composition,
e.g. for fueling an ~nternal combustion engine, comprising a major
amount of hydrocarbons boiling in the gasoline boiiing range; a minor
amount of at least one hydrocarbon soluble compound of a metal
selec~ed ~rom the group consisting of Group VIII metals and mixtures
thereof capable of improving the octane number raeing of the
composition; a minor amount of at least one aliphatic alcohol
containing from about 1 to about 8 carbon atoms per molecule; and a
minor amount of at least one organic peroxy component containing from
1 to about 20 carbon atoms per molecule, wherein the compound and the
combination of alcohol and peroxy component are present in mutually
lZ~Z~;~'7
activating amounts to $mprove the octane number rating o~ the fuel
composition.
We have now found that hydrocarbon fuels for spark ignition
internal combustion engines can be upgraded, that is to say that one
or more of the aforesaid desirable characteristics can be improved, by
reacting the fuel with a hydrocarbyl hydroperoxide.
Accordingly the present invention provides a process for
upgrading a hydrocarbon fuel for a spark ignition internal combustion
engine which process comprises reacting the hydrocarbon fuel with a
hydrocarbyl hydroperoxide at a temperature greater than the
decomposition temperature of the hydrocarbyl hydroperoxide and at a
pressure sufficient to maintain the reactants in the liquid phase.
As the hydrocarbon fuel there may be used a gasoline, i.e. a
peeroleum dis~illate, normally boiling up to 200C. Suitably the
gasoline may be, for example, a straight run gasoline, that is a
gasoline fraction produced directly from crude oil by distillation but
not cracked or reformed, or a cat-cracked spirit, that is a gasoline
fraction obtained by catalytic cracking of a heavy hydrocarbon
fraction. Generally, a straight-run gasoline principally comprises
paraffins, aromatics and naphthenes. On the other hand, a cat-cracked
spirit generally comprises olefins, paraffins and aro~atic
hydrocarbons, the paraffins principally comprising isoparaffin6. The
detailed compositions of the aforesald gasolines will depend on the
relative amounts of the princlpal components of the crude oil from
which the gasolines are derived.
The hydrocarbyl group of ~he hydrocarbyl hydroperoxide may
suitably be an alkyl, cycloalkyl, aryl or alkaryl group. Examples of
suitable hydrocarbyl hydroperoxides include t-butyl hydroperoxide,
cumyl hydroperoxide, cyclohexyl hydroperoxide and phenyl ethyl hydro-
peroxide, of which t-butyl hydroperoxide is preferred. Hydrocar~yl
hydroperoxides may be prepared in known manner by oxidation of the
corresponding hydrocarbon, for example t-butyl hydroperoxide may be
prepared by the oxidation of i~obutane. The molar ratio of
hydrocarbyl hydroperoxide to ~he hydrocarbon fuel reactant may be
varied over a wide range. For high utilisation of the hydroperoxide
~2~%92~7
reactant, low standing concentrations o~ the hydroperoxide are
preferred.
In a preferred embodiment the process of the invention is
operated in the absence of a metal catalyst active for the
deco~position of hydrocarbyl hydroperoxides, Problems associated wlth
the separation and recovery of a catalyst are thereby avo~ded.
It can be advantageous in certain c$rcumstances to effect the
reaction of the hydrocarbon fuel with the hydrocarbyl hydroperoxide in
the presence of solids generally regarded as inert as catalysts for
the decomposition of hydrocarbyl hydroperoxides. Suitable solids
include clays and aluminosilicate zeolites, which may be natural or
synthetic, active carbons and refractory oxides, for example silica,
alumina or silica~alumina.
In another embodiment, the process of the present invention is
operated in the presence of a catalyst active for the decomposition of
hydrocarbyl hydroperoxides. The catal~st for the decomposition of
hydrocarbyl hydroperoxides may suitably be one or more of the metals
rhodium, ruthenium, chromium, platinum, palladium, rhenium, thallium,
thorium, manganese, cobalt, iron, zirconium, nickel, zinc, caesium,
copper, antimony bismuth, lead, arsenic, molybdenum, vanadium,
tungsten and titanium in elemental or compound ~orm. Preferred ~etals
include rhodium, ruthenium, chromium, cobalt, iron and manganese.
Although the metal in finely divided form may be employed, it is
preferred to use a compound, suitably a salt or a complex, of the
metal. Suitable compounds of the metals include the carbonyls,
acetates, acetyl-acetonates, porphyrin complexes, phthalocyanine
complexes and the 1,3-bis(pyridylamino) isoindolines. The process may
suitably be operated in the liquid phàse using a catalyst soluble ln
the reaction mixture or in the liquid phase using an insoluble
catalyst suspended therein or ~n the liquid phase using a supported
catalyst. Suitable supports include refractory oxides, such as
silica, alumina and silica-alumina, aluminosilicate zeolites, clays
and active carbon. The supported catalyst may be prepared by any
suitabie conventional technique, such as by impregnation from an
aqueous or organic solution, ion-exchange, precipitation and
9~
co-precipitation. It i8 preferred to use a supported catalyst in the
form for example oE a fixed bed, a moving bed or a fluidised bed, The
amount of catalyst added in a batch process may suitably be in the
range from O.OOl to 10%, preferably from 0.01 to 5% by weight, based
on the total weight of the reactants.
The process muse be operated at a temperature above the
decompositlon temperature of the hydrocarbyl hydroperoxide. The
particular temperature employed will depend on the nature of the
hydrocarbyl hydroperoxide to be used. Generally, in the absence of a
catalyst for the decomposition of hydrocarbyl hydroperoxides the
temperature will be greater than 125C. Using t-butyl hydroperoxide9
for example, the temperature may sultably be in the range from 125 to
250~C, preferably from 150 to 225G~ It will be appreciated by those
skilled in the art that the presence of a catalyst for the
decomposition of a hydrocarbyl hydroperoxide may considerably lower
the decomposition temperature. Although it may be possible to employ
atmospheric pressure using higher boiling hydrocarbon fuels and lower
reaction temperatures, it will usually be necessary to use elevated
pressures in order to maintain the reactants in the liquid phase.
Since it is possible that not all the hydrocarbyl hydroperoxide
added will be consumed in the process of the invention,
particularly when the process is operated in the presence of a
catalyst for the decomposition of hydrocarbyl hydroperoxides, in a
final step the temperature may be raised above the reaction
temperature for a period such as to effect decomposltion of the
hydroperoxide.
The inventlon may be operated batchwise or continuously,
preferably continuously.
Oxygenated hydrocarbons, particularly hydroxylaeed and ketonised
paraffins, can result fom participation of the alkanes component-of
the fuel in the decomposition of the hydroperoxide to the
corresponding alcohol. Oxygenated hydrocarbons, as is well-kDown, can
increase the octane rating of fuels in which they are present.
Furthermore, the alcohol formed by decomposition of the hydroperoxide
can boos~ the octane rating. For example, t-butanol, formed by
:~zu%g~
can boost the octane rating. For example, t-butanol, formed by
decomposition of t-butyl hydroperoxide, is a known fuels supplement.
The olefins component of the fuel, too, can participate in the
reaction to give oxygenated products.
The invention will now be illustrated by reference to the
following Examples. In the Examples the abbreviations 'TBA and
'TBHP' represent tertiary-butyl alcohol and tertiary-butyl
hydroperoxide respectively.
Octane Ratings were determined by the CFR engine test method
according to ASTM D2699 and D2700 on 10% vol. blends in an aromatic
basestock.
Example 1
lOOml of a mixture of a straight-run gasoline and TBHP (65% w/w
solution in TBA) were mixed in ~ weight ratio of 3.5:1 and heated
together for 2 hours at 200C in a 200ml stainless steel autoclave.
Thereafter the bomb was allowed to cool and the RON and MON of the
resulting product were measured. The values of the RON and MON
obtained are given in the Table.
~xample 2
The procedure of Example 1 was repeated except that the weight
ratio of straight-run gasoline to TBHP was reduced to 2:1.
Comparison Test 1
The straight-run gasoline as used in Example 1 was mixed with TBA
in an amount e~uivalent to the amount that would be formed by complete
decomposition of TBHP in the proportion as used in Example 1 into
TBA. The mixture was heated at 200C for 2 hours in a 200ml stainless
steel aucoclave. The bomb was then allowed to cool and the RON and
MON of the resulting mixture determined.
Example 3
- 30 lOOml of a mixture of the straight-run gasoline as used in
Example 1 and TBHP (65% solution in TBA) were mixed in a weight ratio
of 3.5:1 and heated together for 16 hours at 80C in the presence of a
5% platinum on alumina catalyst (0.5g). The catalyst was filtered off
and the mixture was heated in a 200ml stainless steel autoclave for
2 hours at 200C to decompose any residual dialkyl peroxides. The
product were measured.
Example 4
The procedure of Example 3 was repeated using a 5% ruthenium on
alumina catalyst (0.5g) in place of the platinum on alumina
catalyst.
The RON and MON results for Examples 2 to 4 and Comparison
Test 1 together with the RON and MON figures for the untreated
straight-run gasoline are given in the following Table 1.
TABLE 1
~xample Research Octane Motor Octane Improvement*
No No
(RON) (MON)
1 78.4 77.9 7.95
2 80.5 81.9 11.0
Comp. Test 1 76.3 72.2 4.05
3 75.7 76.5 5.9
4 75.7 79.7 7.5
20Straight-run 70.9 69.5
gasoline (SRG)
*I~LOV. nt = (RoNmeasured-RoNsRG) + (MONmeasured-MoNsRG)/2
The improv~ nt S in octane ratings obtained in the absence of a
catalyst for the decomposition of the hydroperoxide (cf Examples 1
and 2) are comparable with or better than those obtained using a
catalyst at lower temperatures (cf Examples 3 and 4).
Moreover these improvements are obtained over considerably shorter
reaction periods. All the Examples demonstrate an improvement in
octane rating over ~omparison Test 1.
Example 5
t-Butyl hydroperoxide (20 cm3 of 8.5 M t-butyl hydroperoxide in
t-butanol) was added dropwise over 0.5 hour to a stirred flask
containing a straight-run gasoline (100 cm3) and Fe(II)(Tpp)~2~HF
(0.2g) under an inert atmosphere of nitrogen. The resulting
solution was stirred for 16 hours and transferred to an autoclave.
The autoclave was heated for 16 hours at 200C and cooled. The
resulting solution was filtered to re~ove the decomposed catalyst.
The filtrate gasoline was analysed by GLC and its octane ratings
determined~ The results of the octane rating determinations are given
in the Table.
The treated gasoline was shown to contain numerous oxygenates
corresponding to the oxidation products of the initial constituents of
the gasoline. Principal amongæt these were:-
pentan-2-one
2-methyl butan-2-ol
various C6 alcohols
cyclohexanol
cycloheptanol
3-methyl cyclopentanone
methyl phenyl ketone
Example 6
The procedure of Example ~ was repeated except that
Fe(II)(Tpp).2THF was replaced by Fe(III)(Tpp)Cl (0.2g).
Example 7
The procedure of Xxample 5 was repeated except that
Fe(II)(Tpp).2THF was replaced by 10% ruthenium supported on carbon
(0.lg).
Comparison Test 2
The Research Octane No (RON) and Motor Octane No (MON) of the
straight-run gasoline (SRG) as used in Examples 5 to 7 were
determined~ The RON was 65.6 and the MON was 64.4.
Comparison Test 3
t-Butanol (20 cm3) was added dropwise to a solutlon of the
straight-run gasoline as used in Exa~ples 5 to 7 (100 cm3) containing
Fe(III)(Tpp)Cl (0.2g). The solution was stirred for 16 hours and
thereafter the procedure of Example 5 was employed.
This is not an example according to the present invention
- 30 because hydrocarbyl hydroperoxide was not added. It is include~ for
the purpose of comparison only.
The results of the octane rating determinations for Examples 5 to
7 and Comparison Tests 2 and 3 are given in Table 2.
y
Table 2
Example Re search Octane Motor Octane Improvement*
No (RON) No (MON)
79.8 74.111.95
6 75.4 72.08.70
7 76.4 70.88.60
Comp Test 2 65.6 64.4
Comp Test 3 74.9 68.0 6.45
*Improvement =
Nmeasured~ RON SRG) + (MNmeasured~ MONSRG)/2
It can be seen from the results in Table 2 that addition of
t-butanol alone leads to an improvement in octane rating. The
20 improv~ -nt in octane rating resulting from catalytically decomposing
t-butyl hydroperoxide in the gasoline is in excess of that ascribable
to the formation of t-butanol.
3()
- 35
